The Protective Effects Of Grape Seed Extract Against Diabetic Retinopathy And Underlying Mechanisms

Diabetic retinopathy(DR)is the most common serious complication of diabetes.At the early stage of DR,high glucose induces oxidative stress,which increases Müller cells' reactivity and promotes the expression of pro-inflammatory cytokines.Dietary intervention with antioxidants is a safer way for prevention and control of DR.Grape seed extracts(GSE)containing plenty of polyphenols have strong anti-oxidative and anti-inflammatory activities.However,its potential molecular mechanisms involved in anti-inflammatory activity in retina remain unclear.To investigate the protective effect of GSE against hyperglycemia-induced injury in Müller cells,both rat primary Müller cell model and diabetic rat model were established.1.GSE significantly inhibited the inflammation in rat primary Müller cells induced by high glucose.The results of Real-time PCR and ELISA demonstrated 10 ?g/mL GSE significantly down-regulated the expression and secretion of vascular endothelial growth factor(VEGF)in Müller cells exposed to high glucose.Moreover,GSE significantly decreased the mRNA expression of IL-6 and Müller cells' reactive marker,GFAP.2.GSE significantly inhibited morphometric changes of retina in diabetic rats.Systematic morphometric examination of HE-stained paraffin sections showed that the retina thicknesses and ganglion cell numbers were all significantly reduced in Streptozotocin(STZ)-induced diabetic rats compared with the control group.However,the changes of retinal thicknesses and the loss of ganglion cells had been clearly circumvented by the administration of GSE at dose of 200 mg/kg/day.3.GSE had a significant inhibitory effect on retina inflammation.Real-time PCR analysis showed that mRNA GFAP expression increased in the retina of STZ-induced diabetic rats.Consistently,Immunohistochemi-stry analysis showed the increase in the level of protein GFAP.Besides,Real-time PCR analysis showed the up-regulation of VEGF and pro-inflam-matory cytokines including TNF-??IL-1??IL-6 and MCP-1.In diabetic rats administrated with 200 mg/kg/day of GSE,the expression levels of GFAP?VEGF?TNF-??IL-1??IL-6 and MCP-1 in retina were significantly reduced compared with diabetic groups.4.GSE could activate Nrf2/HO-1/GCLc anti-oxidative pathway in the Müller cells,protecting retina against diabetic injury.Immunofluorescence detection showed the nuclear translocation of Nrf2 in Müller cells of diabetic rats administrated with 200 mg/kg/day GSE.Real-time PCR analysis further demonstrated that the levels of mRNA HO-1 and mRNA GCLc expression were accelerated by GSE.In conclusion,GSE effectively inhibited the inflammation in the retina of diabetic rats through activating Nrf2 and up-regulating HO-1 and GCLc expression in Müller cells.